//return the last added string node and remove it frok the stack
public String Pop()
{
string returnString;
//if the header == null the stack is empty, throw an exception.
if(headpointer == null)
{
throw new NullReferenceException("Cannot pop an EmptyStack, no string to return");
}
//else if the head and tail are the same thing there is only 1 node in the stack, return this and clear the stack.
else if(headpointer == tailPointer)
{
returnString = tailPointer.stringObject;
headpointer = null;
tailPointer = null;
//else there is multiple nodes in the stack, set the return string as the tail node as we aways remove this on in a stack(LIFO).
}else
{
returnString = tailPointer.stringObject;
//first check if there is 2 nodes
if (headpointer.Next == tailPointer)
{
//set the tail pointer to now point at the head, nd the tails .next to null as it no longer point at the node we just removed
tailPointer = headpointer;
tailPointer.Next = null;
}
else
{
//else if there are more than 2 nodes, walk the stack untill you get to the node that's .next is the tail pointer, set the node walker as the tail and set its .next to null
StringNode nodeWalker = headpointer;
while (nodeWalker.Next != null)
{
nodeWalker = nodeWalker.Next;
if (nodeWalker.Next == tailPointer)
{
tailPointer = nodeWalker;
nodeWalker.Next = null;
}
}
}
}
//return the string
return returnString;
}
//Method to push StringNode into stack
public void push(String newString)
{
//create string node and set its sting property to the sting passed in
StringNode newStringNode = new StringNode(newString);
//if the string is null throw and exception
if (newStringNode.stringObject == null)
{
throw new NullReferenceException("Cannot push null string to stack");
}
else
{
//Check stack is empty ,if so point the head and tail at new string node
if (headpointer == null)
{
headpointer = newStringNode;
tailPointer = newStringNode;
//Set the current tail pointers .net to point at the new node and set the new node to be the tail pointer.
}
else
{
tailPointer.Next = newStringNode;
tailPointer = newStringNode;
}
}
}